Monocular machine vision may offer limited capability in detecting operator alertness. The position or movement of an operator may be detected by analyzing a monocular image. However, monocular vision data may be deficient in providing reliable determination of the position or movement of an operator, which may require depth perception to ascertain the three dimensional characteristics of the position or movement of an operator. Operator alertness systems that rely on observation of the eyes of an operator encounter technical difficulties where the operator does not constantly face in a uniform direction (e.g., forward) or where the operator wears eyeglasses. Thus, there is need for a method and system for detecting operator alertness using stereo vision.